Project Summary We propose to establish a ?Center for Male Reproductive Epigenomics? (herein called the ?Center?) in response to the NICHD RFA-HD-19-017. The Center aims to study three key aspects of intergenerational epigenetic inheritance of environmentally-induced epimutations: 1) the impact of lifestyle (diet/activity) on the integrity of the sperm epigenome, 2) the molecular mechanisms underlying transmission of lifestyle- induced sperm epimutations to offspring, and 3) the mechanisms by which inherited epimutations can predispose disease states in offspring. By studying the sperm epigenome of male mice maintained on either a high fat diet without exercise or a normal diet + exercise, or transitioned from the former to the latter, in parallel with that of obese, inactive men maintaining an unhealthy lifestyle or transitioned to a healthy diet + exercise lifestyle, we will test our central hypothesis, i.e., paternal epigenetic inheritance of lifestyle-induced metabolic disorders is achieved through a combinatorial molecular mechanism involving sncRNAs, DNA methylation and histone modifications, which relay epimutations from somatic cells to sperm and from a father?s sperm to his offspring where they predispose development of disease-related traits. Our studies in men (Project 1) will establish the extent of the deleterious effects of an unhealthy lifestyle (high fat/caloric diet and physical inactivity) on the human sperm epigenome and will determine whether the incidence of these epimutations can be reduced if an obese/inactive man adopts a healthy lifestyle (low fat/caloric diet + exercise). Our studies in mice (Projects 2 and 3) will reveal the mechanisms by which an unhealthy lifestyle leads to formation of epimutations in spermatozoa that are subsequently transmitted to, propagated within, and deleterious to male offspring ? based on mechanistic studies that cannot be done in men. In the short term, our studies will elucidate the underlying mechanisms by which an unhealthy lifestyle in men can predispose development of unhealthy phenotypes or disease in their offspring and the extent to which transition from an obese/inactive lifestyle to a healthy diet + exercise lifestyle can mitigate these effects. In the long term, a thorough understanding of how lifestyle-induced epimutations initially occur and are transmitted from a father to his sons (= intergenerational epigenetic inheritance) will form the basis for future investigations into mechanisms underlying the subsequent transmission of lifestyle-induced epimutations to multiple subsequent generations (= transgenerational epigenetic inheritance).